Spinal alignment frame

ABSTRACT

Disclosed is a surgical alignment and distraction frame and associated methods of use that facilitates correction of a sagittal imbalance. The alignment and distraction frame works in conjunction with pedicle screw installation guide assemblies to impart the desired correction. The alignment frame can be utilized to ensure the pedicle screw housings are aligned (to facilitate rod coupling) in concert with the completion of a correction maneuver.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a non-provisional application claiming thebenefit of priority under 35 U.S.C. §119(e) from commonly owned U.S.Provisional Application Ser. No. 61/794,723 filed on Mar. 15, 2013 andentitled “Spinal Alignment Frame,” the entire contents of which ishereby incorporated by reference into this disclosure as if set forthfully herein.

FIELD

The present invention relates to the field of spinal surgery and spinalfixation devices, including a system and associated methods formanipulating, distracting and/or reorienting vertebrae of the spine inconjunction with the installation of a spinal fixation construct.

BACKGROUND

The spine is formed of a column of vertebra that extends between thecranium and pelvis. The three major sections of the spine are known asthe cervical, thoracic and lumbar regions. There are 7 cervicalvertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae, with each ofthe 24 vertebrae being separated from each other by an intervertebraldisc. A series of about 9 fused vertebrae extend from the lumbar regionof the spine and make up the sacral and coccygeal regions of thevertebral column.

The main functions of the spine are to provide skeletal support andprotect the spinal cord. Even slight disruptions to either theintervertebral discs or vertebrae can result in serious discomfort dueto compression of nerve fibers either within the spinal cord orextending from the spinal cord. Disruptions can be caused by any numberfactors including normal degeneration that comes with age, trauma, orvarious medical conditions. If a disruption to the spine becomes severeenough, damage to a nerve or part of the spinal cord may occur and canresult in partial to total loss of bodily functions (e.g., walking,talking, breathing, etc.). Therefore, it is of great interest andconcern to be able to treat and correct ailments of the spine.

When conservative efforts fail, treating spinal ailments very oftenincludes one of or a combination of spinal fusion and fixation.Generally, spinal fusion procedures involve removing some or all of anintervertebral disc, and inserting one or more intervertebral implantsinto the resulting disc space. Introducing the intervertebral implantserves to restore the height between adjacent vertebrae (“disc height”)and maintain the height, and/or correct vertebral alignment issues,until bone growth across the disc space connects the adjacent vertebralbodies. Resection of ligaments and/or boney elements from the affectedspinal area is also common in order to access the disc space and/ordecompress impinged nerve or spinal cord tissue.

Fixation systems are often surgically implanted during a fusionprocedure to help stabilize the vertebrae to be fused until the fusionis complete or to address instabilities (either preexisting or createdby the fusion or decompression procedure itself). Fixation constructs ofvarious forms are well known in the art. Most commonly, the fixationconstruct is a plate anchored to the anterior column with multiple boneanchors or a posterior fixation construct including multiple anchors anda connecting rod anchored to the posterior elements of the spine. For aposterior fixation construct the anchors (typically pedicle screws) areanchored into the pedicles of each vertebra of the target motionsegment. The pedicle is a dense, strong, stem-like structure thatprojects from the posterior side of the vertebral body. The anchors arethen connected by a fixation rod that is locked to each anchor, thuseliminating motion between the adjacent vertebrae of the motion segment.The fixation anchors utilized in posterior fixation constructs generallyinclude an anchor shank and a rod housing. The rod housing includes apair of upstanding arms separated by a rod channel in which the fixationrod is captured and locked. When constructing the posterior fixationconstruct the surgeon must align and seat the rod in the rod channel.This can be a challenge as it requires the rod channels of adjacent rodhousings to be generally aligned, or alternatively, the rod must be bentto fit.

In addition to simply stabilizing the spine, components of the fixationsystem can also be utilized to manipulate the positioning of thevertebrae to achieve the desired alignment before movement is arrested.That is, applying a directional force to the anchor shank through theattached housing, for example, via minimally invasive guides, reductiontools, or other instruments that are commonly engaged to the housing andextend out of the patient, causes the associated vertebra to translateor rotate in the direction of the force, thus allowing the surgeon goodcontrol to manipulate the relevant vertebrae into a desired position.However, doing so typically causes the rod housings to move relative toeach other. Thus, achieving the desired correction (realignment) of thevertebrae while also aligning the rod channels of the housings toeffectively seat a rod is a significant challenge and can createdifficulties and delays during the surgery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a spinal fixation system applied to alumbar spine and having coupled thereto one example embodiment of aspinal alignment frame for facilitating manipulation of spinal anatomyto correct spinal imbalances;

FIG. 2 is a perspective view of the alignment frame of FIG. 1;

FIGS. 3A through 3C depict various perspective views of a left-sideindicating and readout arm of the spinal alignment frame of FIG. 1;

FIG. 3D is an exploded view of the indicating and readout arm andrelated frame structure of FIG. 3A;

FIGS. 4A through 4D depict various perspective views of a right-sideindicating and readout arm of the spinal alignment frame of FIG. 1;

FIG. 4D is an exploded view of the indicating and readout arm andrelated frame structure of FIG. 4A;

FIG. 5 is a perspective view of the spinal alignment frame of FIG. 2,with left and right indicator arm assemblies detached from the frame;

FIG. 6 is a perspective view of the backside of the spinal alignmentframe of FIG. 5 the frame; and

FIG. 7 is a flowchart denoting example steps of a method for performinga surgical procedure with the posterior fixation system and alignmentframe of FIG. 1 to perform a surgical correction.

DETAILED DESCRIPTION

Various embodiments disclosed herein include surgical measurement framesthat can be conveniently used by a surgeon to determine an appropriatesurgical correction for a patient suffering from a spinal instability ordeformity. For example, the surgical measurement frame may be used torealign sagittal balance during compression fracture reduction, VBRresection, pedicle subtraction osteotomy (PSO), scoliosis correction, orother procedures affecting sagittal balance.

With reference to FIG. 1, there is shown a spinal fixation construct 10and associated installation guide assemblies 20, coupled with an exampleembodiment of a spinal alignment frame 100. The spinal fixationconstruct is of a type commonly known in the art and includes a pair ofpedicle screws 12 and a rod 18. The pedicle screws 12 each include a rodhousing 14 and a shank (not pictured) coupled to the housing. Thehousing 14 has pair of upstanding arms separated by a rod channel 16 inwhich the fixation rod 18 is captured and locked with a locking cap (notshown). The housing 14 is coupled to the shank in a manner that permitspolyaxial rotation of the housing 14 relative to the shank. Locking ofthe rod 18 within the housing 14 also locks the housing 14, arrestingfurther movement between the housing and the shank. Additionally, thepedicle screw 12 includes a provisional locking feature, variousdifferent embodiments of which are readily known and available in theart, which permits the housing 14 to be locked (again, arresting furthermovement between the housing 14 and the shank) before locking (orpositioning) the rod 18. The provisional locking feature may be eitherreversible or irreversible.

The installation guide assemblies 20 are also of a type commonly knownin the art and includes a generally tubular body 22 with a distal end 24that releasably couples to the rod housing 14 and a proximal end 26 thatextends out of the patient when the pedicle screw 12 is anchored to thevertebra and the distal end 22 is coupled to the housing 14. A lumen 28extends through the body 22, opening in each of the distal end 24 andproximal end 26. Guide channels 30 passing through the body 20 andopening in the distal end 24, and preferably extending along a length ofthe guide toward the proximal end 26, align with the rod channel 16 whenthe guide and screw are coupled. The installation guides 20 facilitaterod delivery into the rod channels 16 and also facilitate engagement ofvarious instruments with the pedicle screw. For example, a shank drivermay extend through the lumen 28 while coupled to the shank, which alsofunctions as a pseudo provisional lock, as the guide 20 (and thus thehousing 14) is restrained from movement relative to the shank by thedriver. Other instruments, such as a provisional locking tool used toengage (or disengage) the provisional lock, locking caps, and reducersmay also be advanced through the lumen 28 to engage the screw 12.Additionally, the guide assemblies 20 can be manipulated from outsidethe body to impart force on the shank, via housing 14 (with the housing14 locked), to adjust the position of the associated vertebra andachieve a desired surgical correction. By way of example, the guides maybe manipulated to compress, distract, translate, rotate, and/or bend theassociated vertebra relative to other vertebrae. It will be appreciatedthat while installation guides are generally used to facilitateminimally invasive pedicle fixation, the guides 20 (and the alignmentframe 100 with them) may be utilized in open pedicle fixation proceduresas well.

FIG. 2 depicts the spinal alignment and distraction frame 100. The frame100 includes a pair of guide attachment rings 110 and 110A, each ofwhich has an internal opening 115 and 115A sized to fit over a singleguide 20, such as those depicted in FIG. 1. Each of the guide attachmentrings 110 and 110A include anterior openings 120 and 120A foraccommodating a set screw (not shown) or other securement feature thatallows the ring to be “locked” or otherwise secured to a desiredposition on the tubular guide 20. In various embodiments the guide 20may include one or more grooves, notches, depressions or openings on anouter surface that accommodates the set screw (or clip, lever, etc.),allowing the ring 110 and 110A to be secured to a predeterminedlongitudinal and/or rotational position on the guide 20, oralternatively, the set screw may directly engage the outer surface ofthe guide body 22. In various alternative embodiments, attachmentmechanisms other than rings could be utilized to attach the frame to thetubular guides, which could include locking tabs, screw and threadmechanisms, quick release tabs, slide locks, collets, inserts, taper andpress fits or other connecting arrangements known in the art. Forexample, one alternative attachment mechanism includes attachment via acap that clips onto the top of the tubular guides, or that could engagea projection, slot, ring or other feature on or extending outward of theguides.

FIGS. 3A through 3D and 4A through 4D depict various perspective andexploded views of the indicating and readout arms and related framestructures. As best seen in FIGS. 3D and 4D, each ring 110 and 110Aincludes an attached ring shaft 125 and 125A. The ring shafts 125 and125A are sized and configured to fit into corresponding openings 130 and130A in first and second attachment blocks 135 and 135A attached to theframe (not shown). Each ring shaft 125 and 125A includes a grooved orreduced diameter section 140 and 140A that accommodates set screws 145and 145A that secure through openings 150 and 150A in the attachmentblocks 135 and 135A. The set screws 145 and 145A allow the ring shafts125 and 125A to be inserted into the openings 130 and 130A and then theset screws 145 and 145A can be tightened a sufficient degree to retainthe ring shafts 125 and 125A within the openings 130 and 130A in thefirst and second attachment blocks 135 and 135A, yet allow the ringshafts 125 and 125A to rotate freely about the longitudinal axes of thering shafts 125 and 125A.

Each ring shaft 125 and 125A includes an indicator arm 155 and 155Awhich is secured to the ring shaft 125 and 125A by a pin 156 and 156A orother feature extending through the ring shaft 125 and 125A. The pin 156and 156A desirably locks the indicator arm to the ring shaft such thatrotation of the ring 110 and ring shaft 125 concurrently displaces androtates the indicator arm 155 and 155A.

Readout arms 160 and 160A are secured to each of the first and secondattachment blocks 135 and 135A by pins 136 and 136A, adhesives or otherattachment features known in the art. Each readout arm 160 and 160Aincludes an opening 165 and 165A through which the respective ring shaft125 and 125A can extend. An indicator scale 170 and 170A is included oneach readout arm 160 and 160A. Because the readout arms 160 and 160A aresecured to the blocks 135 and 135A, the readout arms 160 and 160A do notrotate with the ring shafts 125 and 125A, but rather are securedrelative to the frame (not shown) to which the blocks 135 and 135A areattached. Because the readout arms 160 and 160A remain stationaryrelative to the frame, and the indicator arms 155 and 155A move with thering shafts 125 and 125A, rotation of the rings 110 and 110A relative tothe frame will rotate the indicator arms 155 and 155A relative to thereadout arms 160 and 160A, and the relative rotational position betweeneach indicator arm 155 and a corresponding readout arm 160 can bedetermined from each indicator scale 170 and 170A.

FIG. 5 depicts the measuring and distraction frame 100 assembly, showingleft and right indicator arm assemblies 180 and 180A (i.e. rings, ringshafts, indicator arms, and associated coupling features) prior toinsertion of the ring shafts 125 and 125A into the openings 130 and 130Ain the first and second attachment blocks 135 and 135A. It should beunderstand that “left” and “right” are used for convenience only, andthat various other embodiments could include reversed or otherpositioning arrangements for the various components described herein. Inaddition, the substitution of “left” and “right” with “first” and“second” or “cephalad” and “caudad,” or other such conventions, could beused as desired, and are contemplated herein.

In one exemplary embodiment, the ring 110 of the left indicator armassembly 180 can be slid over or otherwise engaged to a guide 20 and thering shaft 125 inserted into the opening 130 in the first attachmentblock 135. The set screw (not shown) could then be tightened asufficient amount to secure the ring shaft 125 to the first attachmentblock 135, yet allow the ring shaft 125 to rotate relative to the block135, as previously discussed. Similar actions could be taken with theright indicator arm assembly 180A for another guide 20, which can beconnected to the second attachment block 135A in a similar manner.

FIG. 6 depicts an upper perspective view of the alignment anddistraction frame 100, showing an elongated rack 210, a left housing 215and a right housing 220. The left housing 215 connects the firstattachment block 135 to the elongated rack 210. The right housing 220connects the second attachment block 135A to the elongated rack 210,with the right housing 220 capable of translation along the elongatedrack, such that the spacing between the left housing 215 and the righthousing 220 can be varied. The right housing 220 also includes arotating adjustment thumb screw 230 that rotates a pinion engaged withrack 210 and a selective locking mechanism 240.

The elongated rack 210 includes a linear gear bar or toothed portion 245along one side which extends through the right housing. Inside the righthousing 220, a pinion or circular gear 250 engages with the toothedportion 245, with the circular gear 250 attached to the enlarged driveplate of the thumb screw 230. The selective locking mechanism of theright housing includes a locking tooth 260 at one end which engages withthe toothed portion 245 of the elongated rack 210 to prevent translationof the right housing in an undesirable manner when the lock is engaged.The other end of the locking mechanism includes a push plate 265 whichcan be depressed to overcome the force of a biasing spring 270 thatmaintains the locking tooth 260 in contact with the toothed portion 240of the elongate rack 210.

In this embodiment, to slide the right housing along the elongated rack240, a user can depress the push plate 265, which disengages the lockingtooth 260 from the toothed portion 245. The thumb screw 230 can then berotated in a clockwise or counterclockwise direction, which rotates thecircular gear 250 against the toothed portion 240 of the elongated rack210 and drives the right housing 220 away from or towards the lefthousing. Once movement of the right housing 220 is no longer desired,the push plate 265 can be released, and the locking tooth 260 willre-engage with the toothed portion 245 of the rack 210. The lockingplate itself may include a secondary lock (not shown) that holds thepush plate in the disengaged position to relieve the user of the need tomaintain continuous pressure on the push plate while also operating thethumb screw 230.

In alternative embodiments, the locking mechanism could include avariety of locking and/or unlocking modes, including a “free wheeling”or unlocked mode (i.e., an unlocked mode which allows the right housingto freely slide), a “closing detent” mode (i.e., a detent mechanism thatallows sliding of the right housing towards the left housing, butinhibits motion in the other direction), an “opening detent” mode (i.e.,a detent mechanism that allows sliding of the right housing away fromthe left housing, but inhibits motion in the other direction), a poweredmechanism, linear sliders, and/or any other mechanism desired or known.The unlocked mode could be particularly useful during initial placementof the frame onto the tubular guides, as well as during the variousdistraction and/or correction operations, as it may be desirous toadjust the spacing between the housings to accommodate the initialplacement of the left and right indicator arm assemblies and/or tofacilitate the surgeon's manual movement of the guides 20 duringrotation, distraction/compression and/or other corrective maneuvers.

With reference to FIG. 7, one example method utilizing the spinalalignment and distraction frame 100 to correct a sagittal misalignmentand fixate the correction is described. Initially, in step 300 first andsecond pedicle screws 12 are anchored into a superior vertebral body andan inferior vertebral body that are each adjacent to a fractured,compressed, misaligned, or resected vertebral body located therebetween. The vertebral body may be fractured, compressed, misaligned, orresected due a wide variety of pathologies, including osteoporosis,trauma, metastatic disease or other causes. The pedicle screws 12 areanchored with their respective guides 20 engaged to the housing 14 andextending out of the incision(s) used for installation. Drivers used todrive the screw shanks are left engaged to the shank and extending outof the guide lumen 28. Next the spinal alignment and distraction frame100 is coupled to the installation guides 20 by sliding the ringconnectors 110 and 110A over a respective guide (Step 302).Alternatively, the connection rings 110 and 110A can be attached to theguides 20 first, and thereafter the ring shafts 125 and 125A can becoupled to the frame. The frame permits one or more of the ringconnectors to slide relative to the frame, allowing the spacing betweenthe rings to be widened and/or narrowed as needed, and facilitating thesliding of the ring connections over the guides 20 (and drivers) andengaging set screws through the apertures 120 and 120A. For step 304,with the ring connectors 110 and 110A unlocked (that is, able to rotaterelative to the frame), an initial angle reading is taken for eachguide/ring connector combination. For example purposes, initial readingswill be denoted as A^(I) and B^(I), with A^(I) representing an anglevalue between the axis of the ring connector 110 (and attached guide 20)and the rack, and B^(I) representing an angle value between the axis ofthe ring connector 110A (and attached guide 20) and the rack. Initialangle readings are noted for future reference. With the drivers sillengaged to the screw shanks (to in essence effect a provisional lockingof the housing 14 relative to the shank), the guides 20 are manipulatedto achieve the desired realignment or correction of the vertebrae (step306) (which can be monitored or verified using fluoroscopy or othervisualization techniques). When the desired correction is achieved,corrected angle readings are taken, denoted as A^(C) and B^(C) (forexample purposes), from the readout indicators 170 and 170A (step 308).The readings A^(C) and B^(C) represent the angle of the respectiveguides 20, and thus the housings 14 also, relative to the rack 210. Instep 310 the total angulation values needed to achieve the desiredcorrection is determined, denoted herein (for example purposes) as A^(T)and B^(T). A^(T) and B^(T) are determined by calculating the deltabetween the corrected angle readings (A^(C) and B^(C)) and the initialangle readings (A^(I) and B^(I)), respectively. This can be accomplishedby subtracting A^(C) from A^(I) and B^(C) from B^(I). Thus for examplepurposes only, if A^(I) equals negative 3 and A^(C) equals negative 8,then A^(T) equals positive 5. Likewise, if B^(I) equals positive 2 andB^(C) equals negative 4, the B^(T) equals positive 6. (In step 312, thecorrection may be released, and the drivers removed from the guides 20(effectively unlocking the housing 14 relative to the shank). With thehousings 14 free to move relative to the shanks, in step 314 the guides20 are again manipulated, this time to align the guides 20 with theangle readings A^(T) and B^(T). While maintaining the angles A^(T) andB^(T), the provisional locking feature of the screws 12 is engaged (step316), locking the housings relative to the shanks in the positions A^(T)and B^(T). This may be accomplished, for example, by advancing aprovisional locking tool through the lumen 28 of each guide and engagingthe locking mechanism.

Moving to step 318, the guides 20 are manipulated again, this time tomaneuver the guides to the zero angle position. This adjustment to zerowill provide the desired correction while simultaneously aligning thehousings 14 generally parallel to each other such that the rod 18 can bepassed (step 320) without custom bending and locked in place withlocking caps.

Prior to locking the rod completely, the surgeon may also choose to lockthe ring connectors 110 and 110A such that the rack may be utilized toapply parallel compression or distraction to the vertebrae by operatingthe thumb screw 230 to translate the housing 220 along the rack 210 inthe appropriate direction. Once the final desired corrections and/orspinal alignment have been obtained (which may include desired lordoticor other curvature corrections, at the surgeon's options) the rod isfinally locked. The frame 100 and guides 20 are disengaged and removed.

The disclosed system desirably provides for the accurate alignment andlocking of polyaxial screw heads in desired rotational positionsrelative to their respective screw shanks already implanted intovertebral bodies in such a manner that later distraction and/orreduction of the vertebral bodies to a desired orientation can beaccomplished using distraction, torque and rotational forces on thevertebral bodies through the attached pedicle screw shanks, with theresulting alignment of the pedicle screw heads being optimized forsecurement to a longitudinal spinal rod or other instrumentation withoutrequiring bending of the rod or the use of specialized adapters. Thedescribed frame also facilitates the distraction and/or compression ofthe relevant spinal segment in a controlled fashion after a surgicalcorrection and/or appropriate lordosis/curvature of the spine has beenobtained but before final fixation of the spinal anatomy usinginstrumentation has been accomplished.

While specific embodiments have been shown by way of example in thedrawings and described herein in detail, it will be appreciated that theinvention is susceptible to various modifications and alternative forms(beyond combining features disclosed herein). The description herein ofspecific embodiments is not intended to limit the invention to theparticular forms disclosed, but on the contrary, the invention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

What is claimed is:
 1. A spinal alignment frame for facilitatingalignment of vertebrae in the spine of a patient in conjunction with theinstallation of a spinal fixation construct, the spinal fixationconstruct including a pair of pedicle screws each including an anchorand a polyaxial housing that rotates relative to the anchor and aconnecting rod that couples between the housings, each of the housingsalso being releasable coupleable to a screw extension instrument thatextends out of the patient from the housing, the spinal alignment framecomprising: an elongated rack, a first coupler coupled to the rack andincluding a first attachment ring coupled to a cylindrical shaft, theattachment ring sized to receive a screw extension instrument, and asecond coupler coupled to the rack and configured to be releasablycoupled to a guide, wherein the first coupler is rotatable relative tothe rack and includes an indicator that indicates an angle of the firstcoupler relative to the rack, and wherein the second coupler isrotatable relative to the rack and includes an indicator that indicatesan angle of the second coupler relative to the rack, at least one of thefirst coupler and the second coupler being translatable along the rack;wherein the first coupler indicator includes a first readout armpermanently attached to the rack and a first indicator arm removably androtationally fixed to the first attachment ring; wherein the firstreadout arm includes a housing having a cylindrical cavity, the housingfurther includes a set screw that advances into a groove of thecylindrical shaft that aligns with the set screw when the cylindricalshaft is positioned in the cylindrical cavity such that attachment ringis freely rotatable within the cavity and translationally fixed withinthe cavity.
 2. The spinal alignment frame of claim 1, wherein the firstattachment ring includes a lock for fixing the position of the firstattachment ring relative to the screw extension instrument.
 3. Thespinal alignment frame of claim 1, wherein the first coupler includes afirst cap configured to receive a proximal end of the screw extensioninstrument.
 4. The spinal alignment frame of claim 1, wherein the secondcoupler indicator includes a second readout arm rotational fixed to therack and a second indicator arm rotational fixed to the secondattachment ring.
 5. The spinal alignment frame of claim 1, wherein theelongated rack includes a toothed portion.
 6. The spinal alignment frameof claim 5, wherein the second coupler includes a pinion which engageswith the toothed portion.
 7. The spinal alignment frame of claim 5,wherein the second coupler includes a locking tooth which engages withthe toothed portion to prevent translation of the second coupler.
 8. Thespinal alignment frame of claim 7, further comprising a push plate whichwhen pushed serves to disengage the locking tooth from the toothedportion to enable translation of the second coupler.
 9. The spinalalignment frame of claim 7, wherein the locking tooth and the toothedportion are engaged using a biasing spring, which force is overcome bypushing of the push plate.